Isolated spermatogenic cells will not differentiate into sperm. In vivo all stages of spermatogenesis develop in continuous contact with the Sertoli cell surface. Stem cell proliferation and initiation of meiosis additionally occur in contact with the seminiferous spermatogenic cells both the Sertoli cell surface and extracellular matrix (ECM) components affects spermatogenic cell differentiation. A better understanding of the factors necessary for spermatogenic cell differentiation should lead to better diagnosis and treatment of male infertility. The specific aim of this grant is to identify and characterize the spermatogenic cell- surface macromolecules responsible for adhesion to both Sertoli cells and the testicular basement membrane. An immunological approach will be taken to identify the spermatogenic cell-surface receptors responsible for binding to Sertoli cells in vitro has been developed. The spermatogenic cell plasma membrane subfraction which specifically neutralizes the inhibitory effect of the antiserum will be used as an immunogen for the production of specific antisera to spermatogenic cell surface adhesion molecule(s). A variety of criteria will be used to confirm that the antigens recognized are involved in spermatogenic cell-Sertoli cell adhesion. The ECM components to which spermatogonia and early spermatocytes bind will be determined through the use of solid phase adhesion assay systems. The identified ECM components will then be used to isolate the receptors of spermatogenic cells by affinity chromatography. Once the cell adhesion receptors of spermatogenic cells have been identified, then the effects of ligand binding on differentiation can be studied.